Packaging is the technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a coordinated system of preparing goods for transport, warehousing, logistics, sale, and end use. Packaging contains, protects, preserves, transports, informs, and sells.
Stretch wrap or stretch film is a highly stretchable plastic film that is wrapped around items. The elastic recovery keeps the items tightly bound. In contrast, shrink wrap is applied loosely around an item and shrinks tightly with heat. It is frequently used to unitize pallet loads but also may be used for bundling smaller items. The process provides a film around one or more products with the aim to stabilize protect and secure the cargo from tampering or theft.
Types of stretch film include bundling stretch film, hand stretch film, extended core stretch film, machine stretch film and static dissipative film. The most common stretch wrap material linear low-density polyethylene or LLDPE, which is produced by copolymerization of ethylene with alpha-olefins, the most common of which are butene, hexene and octene. The use of higher alpha-olefins (hexene or octene) gives rise to enhanced stretch film characteristics, particularly in respect of elongation at break and puncture resistance. Other types of polyethylene and PVC can also be used. Many films have about 500% stretch at break but are only stretched to about 100-300% in use. Once stretched, the elastic recovery is used to keep the load tight. Other properties such as break strength, cling, clarity, tear resistance, static discharge, etc. are also important.
In pallet unitizing, stretch wrap can have several functions including improved stability of products or packages, forming a unit load, more efficient handling and storage of unit loads, dust and moisture protection, tamper resistance and resistance to package pilferage, sun protection (UV stretch wraps). Ensuring cartons stay on the pallet is an important consideration in warehouse distribution, especially as the demands for increased throughput continues to rise.
There are two main methods of the pallet wrapping process; the vertical and the horizontal. The highly stretchable film is wrapped around the item while adjusting the tension, the film provides secondary protection. Other products which can't resist the tension of the film can, in principle, be damaged. It is thus important that the product packaging is stabilized and maintained before and during the wrapping process.
Categories and sub-categories of stretch wrappers include manual, semi-automatic and automatic wrappers.
Automatic wrappers can include a conveyor system to automatically load the wrapping machine and automatic systems to apply, seal, and cut the film. Types of automatic wrappers include:
Turntable wrappers; the load to be wrapped sits on a turntable which spins the load relative to the film roll, which is housed in a carriage which can move up and down a fixed “mast”. Stretch is achieved by rotating the load at a faster rate than the film is fed.
Rotary arm wrappers; the load remains still while a rotating arm turns around it wrapping the load. This system is used for light loads or for speeds which would otherwise cause the load to topple due to high rotation speeds.
Rotary ring wrappers; the film is housed in a carriage on a horizontal ring in which the load remains static while the horizontal ring is rotating around the load and moves up and down vertically relative to the load, similar to a rotary arm stretch wrapper. The rotary ring technology can be a more balanced system with less wear and maintenance than the other available wrapping technologies. These wrappers are capable to reach the highest production capacities (up to 160 pallets/hour).
Calculation of pallet wrapping cost is critical to any manufacturing operation using any type of wrapper. Wrapping costs can be in the millions of dollars per year, thus cost and efficiency are essential parameters for management of business operations.
Typically, calculation of wrapping costs is a laborious, inefficient, and time-consuming operation. For example, a user might normally wrap a pallet, remove the film, wad it in a ball and weight it. Next, the user would calculate the number of pounds of material on each roll of stretch wrap film by using an industry standard formula for e.g. a roll with a 3″ core. After converting the number of pounds to ounces, the user calculates the number of wrapped pallets per roll of film. Finally, the cost to wrap one pallet is calculated by dividing the cost per roll by the number of wrapped pallets per roll. This manual method is time consuming, inaccurate, and does not provide real time data to a user.
There are limited ways to determine the amount of film being used by a stretch wrapping machine. After a machine is adjusted, the adjustments can change. When an owner of a stretch wrapping machine sets up the machine, they expect the film costs to remain constant and expect the stability of the palletized loads to remain constant as well. In reality, machine wear or unauthorized adjustments made by personnel can alter machine function. Typically, the loads may appear to become less stable and the operators may adjust the machine to apply more film to the loads. In turn, this action can increase film costs as well as increase the amount of waste.
Weight differences between measured roll weights are used in part to calculate the cost per load wrapped. The purpose of utilizing this method for determining the cost per load is based on the currently acceptable load costing method used industry wide called “cut and weigh”.
Thus, a need exists to better measure, monitor, and control the use of stretch film to provide users with accurate real time data. While known systems can perform a film weight test after every load is wrapped, the novel systems disclosed herein can provide real time data to using a machine to machine network or the internet. More accurate information about the consistency of the stretch wrapping process can be available to customers immediately and can include alarms when the process parameters are outside of a user specified range.